Remove M matrix structure from mjData.

Introduced in March 2025 as a temporary measure, this is not considered a breaking change.

PiperOrigin-RevId: 758311298
Change-Id: Ia08857c18b791f6a62a2d8d136b45fc075507b93

mjx/mujoco/mjx/_src/io.py

@@ -627,10 +627,6 @@ def _make_data_c(
       'B_rownnz': (m.nbody, np.int32),
       'B_rowadr': (m.nbody, np.int32),
       'B_colind': (m.nB, np.int32),
-      'M_rownnz': (m.nv, np.int32),
-      'M_rowadr': (m.nv, np.int32),
-      'M_colind': (m.nM, np.int32),
-      'mapM2M': (m.nM, np.int32),
       'C_rownnz': (m.nv, np.int32),
       'C_rowadr': (m.nv, np.int32),
       'C_colind': (m.nC, np.int32),

mjx/mujoco/mjx/_src/io_test.py

@@ -471,7 +471,7 @@ class DataIOTest(parameterized.TestCase):
 
     if backend_impl == 'c':
       # check fields specific to the C implementation
-      np.testing.assert_allclose(d_2.M_rownnz, d.M_rownnz)
+      np.testing.assert_allclose(d_2.bvh_active, d.bvh_active)
 
   def test_get_data_runs(self):
     xml = """

mjx/mujoco/mjx/_src/types.py

@@ -984,10 +984,6 @@ class DataC(PyTreeNode):
   B_rownnz: jax.Array  # pylint:disable=invalid-name
   B_rowadr: jax.Array  # pylint:disable=invalid-name
   B_colind: jax.Array  # pylint:disable=invalid-name
-  M_rownnz: jax.Array  # pylint:disable=invalid-name
-  M_rowadr: jax.Array  # pylint:disable=invalid-name
-  M_colind: jax.Array  # pylint:disable=invalid-name
-  mapM2M: jax.Array  # pylint:disable=invalid-name
   C_rownnz: jax.Array  # pylint:disable=invalid-name
   C_rowadr: jax.Array  # pylint:disable=invalid-name
   C_colind: jax.Array  # pylint:disable=invalid-name